Facial prosthetic model fabrication using rapid
prototyping tools
Chua Chee Kai
Nanyang Technological University, Singapore
Chou Siaw Meng
Nanyang Technological University, Singapore
Lin Sin Ching
Nanyang Technological University, Singapore
Lee Seng Teik
Department of Plastic Surgery, Singapore General Hospital
Saw Chit Aung
Department of Plastic Surgery, Singapore General Hospital
Introduction
It is not uncommon to meet people who
unfortunately have some degree of facial
deformities or disfigurement. The cause of
such a mishap could be accidental from
work, spread of diseases that require the
segregation of healthy tissue from malignant
tissue, or congenital facial deformities that
prevent a person from having a normal facial
anatomy. Some examples of facial
deformities include ± loss of the nose, an ear,
an eye, or portion of the cheek or the lip.
People with such trauma may have to
succumb to criticism, pressure or isolation
from the society and themselves. Their
appearance may discourage them from
mixing with physically normal people.
Hence, the foremost thought of a person so
afflicted is to find some way to restore their
appearance to normal in the shortest possible
time.
Modern plastic surgeons have adopted the
technique of replacing the missing tissue by
one's own skin rather than making an
artificial substitute. Medically, this method
has the advantage of matching the patient's
skin colour to that of the grown tissue. Also,
rejection of tissue can be eliminated and
retention of tissue is neater via surgical
stitching. Yet in some circumstances, it is not
feasible for the following reasons (Bulbulian,
1973):
.
the local condition of the tissue, in the
case of a malignant disease, may be such
that the original lesion is likely to recur
following a surgical procedure and thus
nullify the surgical result;
.
the vascular condition at the site of the
deformity may be so poor because of
previous irradiation that reconstruction
by grafting of tissue involves considerable
risk of sloughing or implanted tissue
dropping off;
.
the loss of tissue may be so extensive that
tissue grafting may not be feasible;
.
the advanced age of the patient may make
him or her a poor candidate for extensive
and multiple surgical procedures;
.
the patient may not be able to afford the
time and expense required by multiple
operations; and
.
the anatomic region to be reconstructed
may require such precision and exactness
of contour that it presents an
insurmountable difficulty from a plastic
surgical standpoint.
Hence, in any event similar to the above-
mentioned circumstances, a prosthetic
restoration must be considered as the only
recourse available to the patient.
Conventional prosthesis-making
technique
There are many surgical modalities to the
making of a prosthesis. A widely adopted
technique is to manually craft the prosthesis,
as shown in Figure 1. The process of
producing crafted prostheses requires
experience, skill and time. Prostheses like an
ear may take weeks to deliver. The process
begins with the use of the plaster-of-Paris
(dental stone) material to mimic the
impression of the defective area, and then
use of hydrocolloid impression material to
mimic the impression of the full normal ear.
The cast of the patient's normal ear is used as
a guide in modelling and shaping the wax
pattern, so that its shape, peculiarities and
character will match those of the patient's
normal ear (Bulbulian, 1973).
Recently, prosthodontists Chambers et al.
(1996) proposed an improved method on
dental stone mould casting. Although the
dental stone moulds are easy to construct,
accurate and inexpensive, they are fragile
and susceptible to breaking during
The current issue and full text archive of this journal is available
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[ 42 ]
Integrated Manufacturing
Systems
11/1 [
2000
] 42±53
# MCB University Press
[
ISSN 0957-6061
]
Keywords
Prototyping, Model,
Integrated manufacturing system,
Health care
Abstract
While computerized tomography
(CT) and magnetic resonance
imaging (MRI) technologies are
highly commendable for their ap-
plications and usage, sometimes
cases involving facial anatomy
restoration may not necessarily
require these highly sophisticated
technologies. A suitable replace-
ment that is also non-contact and
allows fast image capture is the
laser digitizer surface scanner.
This scanner takes only seconds
to capture an image of the pa-
tient's sound or healthy facial
anatomy. By using the captured
image data, it is possible, with the
help of a surface data modeller
rapid prototyping (RP) machine
and vacuum casting machine, to
manufacture the prosthesis for
implant. Presents a novel ap-
proach for facial prosthesis fabri-
cation through a case study of a
prosthetic ear model using an
integrated manufacturing system
comprising the laser surface digi-
tizer, surface data modeller, rapid
prototyping system and vacuum
casting system.
Received June 1998
Revised January 1999
Accepted March 1999